Vent Stuff CCM

Question 1

Name the equation of motion

Answer 1

Pvent + Pmuscles = elastance x volume + resistance x flow

Question 2

How do you use Ohm’s law to calculate the respiratory resistance?

Answer 2

Ohms law
flow = pressure gradient / resistance

resistance = pressure gradient / flow
resistance = driving pressure /flow

Question 3

What variable determines initiation versus termination of inspiration

Answer 3

initiation - trigger variable (patient effort or time)

termination - cycle variable (usually RR + I:E ratio)

Question 4

How can you manually provide PEEP to a patient if the vent doesn’t have this function?

Answer 4

1. connect tube to the exhalation port of the ventilator
2. submerge the end of the tube in the desired depth of water (e.g., PEEP of 5 cm H2O)

Question 5

What is rise time?

Answer 5

time until peak inspiratory pressure is met

Question 6

What PaO2 or SaO2 levels are employed for permissive hypoxemia?

Answer 6

• SaO2 88-95%
• PaO2 55-80 mm Hg

Question 7

How can you determine true PEEP (auto and given PEEP?)

Answer 7

expiratory hold

Question 8

What influences/determines Mean airway pressure?

Answer 8

1. pressure used to overcome circuit and airway resistance
2. pressure used to deform the lung and expand alveoli
3. pressure throughout the expiratory flow phase
4. PEEP

Question 9

How do you calculate static compliance?

Answer 9

= Tidal volume / (Pplat - PEEP)

Question 10

How do you calculate dynamic compliance?

Answer 10

= Tidal Volume / (PIP - PEEP)

Question 11

How do you calculate airway resistance?

Answer 11

Raw = (PIP-Pplat) / airflow
for inspiration

Raw = (Pplat - PEEP) / airflow
for expiration

Question 12

Why are inhalants contrainidcated for anesthesia in ventilated patients?

Answer 12

• inhibits hypoxic vasoconstriction&raquo_space; could worsen V/Q mismatch and therefore oxygenation
• worse immunosuppressive effects than TIVA
• most ventilators are not equipped to give inhalant anesthetic

Question 13

What is the MOA of propofol?

Answer 13

potentiation of GABA-induced chloride-current via GABA-A receptro

Question 14

What are potential adverse effects of propofol?

Answer 14

• apnea
• cardiovascular depression
• transitory myoclonus during induction (rare)
• propofol-infusion syndrome (reported in people, one maybe case report in a dog)
• Heinz-Body anemia in cats (likely only relevat > 24 hours of infusion)
• Lipemia (unlikely)
• prolonged recovery after long-term infusion (24 hours or longer)

Question 15

What are potential adverse effects of alfaxalone

Answer 15

• events at induction and recovery: shaking, tremors, apnea, cyanosis, myoclonus
• apnea
• cardiovascular depression only at high doses

Question 16

What is the MOA of GABA?

Answer 16

binds GABA-A receptors

Question 17

What is the MOA of ketamine?

Answer 17

Dissociative, acts on the following receptors:
* NMDA
* opioid
* monaminergic
* muscarinic

dissociation of the limbic and thalamocortical systems

Question 18

What are adverse effects of Ketamine?

Answer 18

• Delirium during recovery
• accumulation if renal disease
• slower recoveries compared to propofol after 24 hour infusion

Question 19

Why is Etomidate not recommended in vent cases?

Answer 19

prolonged infusion will cause adrenocortical suppression

Question 20

What receptors does dexmed work on and where are they located?

Answer 20

alpha-2 receptors

sedation via binding them in the locus coeruleus and rostroventral lateral medulla –> decreased norepinephrine release

Question 21

What is the MOA of Acepromazine?

Answer 21

D2 dopamine receptor blocker

Question 22

What is the maximum cuff pressure that should be used for the ET tube cuff?

Answer 22

• > 25 cm H2O shown to reduce tracheal blood flow&raquo_space; risk of necrosis
• recommend to stay under 30 cm H2O
• American thoracic society recommends to stay > 20 cm H2O to prevent ventilator associated pneumonia